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<p>Liquid nitrogen fracturing, as an effective coal seam stimulation technology, has received widespread attention and research. The application of liquid nitrogen freeze–thaw cycle can fully utilize its low-temperature damage effect, thereby improving the effectiveness of coal fracturing. Based on relevant experimental results, this article creatively introduces the degradation coefficient of fracture toughness, establishes the initiation standard of coal fracturing cracks under the influence of liquid nitrogen, and derives a fluid solid coupling model under gas fracturing conditions to study the nitrogen fracturing characteristics of coal treated with liquid nitrogen freeze–thaw. The results indicate that with the increase in freeze–thaw cycles, the pore pressure around the borehole gradually increases and the increase slows down after 3 cycles, while the coal fracturing pressure gradually decreases. In addition, the experimental results also proved the accuracy of the simulation, and it was found that the increase in the number of cycles resulted in a greater volume fracture degree after coal fracturing failure. It can be seen that liquid nitrogen circulation freeze–thaw assisted coal seam fracturing is expected to become an effective method for increasing reservoir production.</p>

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Characteristics analysis of nitrogen gas fracturing in coal treated by liquid nitrogen freeze–thaw based on numerical model

  • 期刊论文

  • 发表日期：

    2025年1月28日

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  • Shengcheng Wang,
  • Shanjie Su,
  • Feng Cai,
  • Chunbo Zhou,
  • Menglin Du,
  • Yue Li,
  • Xuan Jiang

摘要

Liquid nitrogen fracturing, as an effective coal seam stimulation technology, has received widespread attention and research. The application of liquid nitrogen freeze–thaw cycle can fully utilize its low-temperature damage effect, thereby improving the effectiveness of coal fracturing. Based on relevant experimental results, this article creatively introduces the degradation coefficient of fracture toughness, establishes the initiation standard of coal fracturing cracks under the influence of liquid nitrogen, and derives a fluid solid coupling model under gas fracturing conditions to study the nitrogen fracturing characteristics of coal treated with liquid nitrogen freeze–thaw. The results indicate that with the increase in freeze–thaw cycles, the pore pressure around the borehole gradually increases and the increase slows down after 3 cycles, while the coal fracturing pressure gradually decreases. In addition, the experimental results also proved the accuracy of the simulation, and it was found that the increase in the number of cycles resulted in a greater volume fracture degree after coal fracturing failure. It can be seen that liquid nitrogen circulation freeze–thaw assisted coal seam fracturing is expected to become an effective method for increasing reservoir production.